NaCl amendment improves vinblastine and vincristine synthesis in Catharanthus roseus: a case of stress signalling as evidenced by antioxidant enzymes activities

An improved synthesis of vinblastine and vincristine was observed in Catharanthus roseus L. (G). Don by using NaCl as an elicitor. Various in vitro grown embryogenic tissues were cultivated under salinity stress for enhanced synthesis of alkaloids. Different levels of salt [ control (0 mM), NT1 (25 mM), NT2 (50 mM), NT3 (75 mM), NT4 (100 mM), and NT5 (125 mM)] were amended in MS and callus biomass growth (fresh-and dry-weight) and biochemical attributes at various embryogenic stages were studied. Maximum callus biomass reduction was observed in 125 mM NaCl amended medium. Antioxidant enzymes i.e. superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase and glutathione reductase activities were assayed as in vitro grown tissues were elicitated with NaCl, causing cellular stress. The antioxidant enzymes activity increased linearly with increasing NaCl level in medium, 4.97 EU min(-1) mg(-1) SOD and 3.14 EU min(-1) mg(-1) CAT, both being maximum in proliferating embryos at NT5. Quantitative estimation and comparative yield of alkaloids were made in response to NaCl stress in different cultivated tissues by using HPTLC method. Vinblastine content was observed to be maximum in regenerated leaves (14.17 mg/g dry wt) on 25 mM NaCl amended medium, followed by in vitro raised shoots. Similarly, better accumulation of vincristine (5.12 mg/g dry wt) was also noted in NaCl amended medium especially at low level (NT1). The data presented indicate that the synthesis of Catharanthus alkaloids was growth specific and was influenced by NaCl levels.